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The influence of low pressure operation on fluidization quality
No full textThe effect of low pressure operation on the fluidization quality of Group B powders has been studied. Pressure fluctuations have been analyzed-using the standard deviation, the power spectral density function (PSDF) and the auto- and cross-correlation functions for operating pressure down to 4 kPa. Low pressures were found to lead to slugging behavior at lower gas velocities than predicted using correlations applicable to higher pressure operation. Although the fluidization quality was found to be little affected by small decreases in pressure below the ambient level, quite drastic decrease on the fluidization quality were observed at the approach to the 4 kPa lower limit investigated in this study. (C) 2003 Elsevier B.V. All rights reserved
Decomposition of Wood Particles in Fluidized Beds
No full textHigh-temperature biomass pyrolysis is the first step of the thermochemical process taking place in a fluidized bed gasifier; it influences strongly the final product gas composition, specifically hydrogen content, as well as tar (heavy organics) production. In this work, the devolatilization of wood particles of controlled size and the combustion/gasification of the remaining char have been studied, as functions of time, in bubbling nitrogen-, steam-, and air-fluidized beds of sand. The influence of particle size, moderate moisture content, bed temperature, and fluidization severity has been investigated experimentally. A semiempirical model, to account for chemical reaction and mass transfer phenomena, has been developed for the devolatilization step. This considers heat transfer to and through the wood particles, and the global wood conversion process described in terms of a single apparent activation energy and a preexponential factor which varies with biomass size. Despite its extreme simplicity, the model is able to provide a remarkably good description of the empirical behavior over the whole range of particle size (5-20 mm) and bed temperature (560-740 °C) explored in the experimental study; its reliable predictions of the overall particle devolatilization time suggest its applicability over a substantially wider interval of variation of these parameters
Pyrolysis and gasification kinetics of biomass particles of different size in a fluidised bed
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Biomass Steam Gasification: Effectiveness of dolomite as raw gas cleaner and heat carrier medium
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Reduction of of tar content by thermal cracking in the fuel gas produced by biomass steam-gasification
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